8.2 Photosynthesis: An Overview

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8.2 Photosynthesis An Overview
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Photosynthesis

• - The process by which plants use the energy from
  sunlight to convert water and carbon dioxide into
  high energy carbohydrates, oxygen.
• The formula
• 6H2O 6CO2 ? C6H12O6 6O2

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Photosynthesis History

• Van Helmont (1643)
• Devised an experiment that led him to conclude
• That a tree gains most of its mass from water
• J. Priestley (1771)
• Using a bell jar, candle, and a plant he
  concluded
• The plant releases oxygen

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• J. Ingenhousz (1779)
• Found that aquatic plants release bubble of
  oxygen in the light but not in the dark
  concluding
• Plants need sunlight to produce oxygen
• The above scientists, led others to discover that
  in the presence of light, plants transform carbon
  dioxide into carbohydrates and they also release
  oxygen.

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The Photosynthesis Equation

• 6H2O 6CO2 ? C6H12O6 6O2
• Photosynthesis is a series of reactions that use
  light energy from the sun to convert water and
  carbon dioxide into sugars and oxygen.

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Lights and Pigments

• In addition to water and carbon dioxide,
  photosynthesis requires light and chlorophyll, a
  molecule in chloroplasts.
• Cliff notes on light
• White all color wavelengths being reflected
  back at you.
• Black all color wavelengths being absorbed and
  none being reflected back at you.
• The color you see is not absorbed but is reflected

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Lights and Pigments

• Pigment light absorbing molecules
• Chlorophyll plants primary pigment
• Chlorphyll a
• Chlorophyll b
• When plants absorb light, the energy is
  transferred directly to electrons in the
  chlorophyll, powering photosynthesis.

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Section Assessment

• 1.  Key Concept What did van Helmont, Priestley,
  and Ingenhousz discover about plants?
• 2.  Key Concept Describe the process of
  photosynthesis, including the reactants and
  products.
• 3.  Key Concept Why are light and chlorophyll
  needed for photosynthesis?
• 4. Describe the relationship between chlorophyll
  and the color of plants.
• 5. Critical Thinking Predicting How well would a
  plant grow under pure yellow light? Explain your
  answer.